In order to test the Java Virtual Machine (JVM), developers often need to manually design or use test generation tools to create complex test programs to detect potential defects in the JVM. However, complex test programs bring high costs to developers in terms of locating and fixing defects. Test program reduction techniques aim to minimize the amount of code in test programs that is unrelated to defect detection, while maintaining the program's defect detection ability. Existing research has achieved good reduction results based on Delta Debugging in C programs and XML inputs, but in the JVM testing scenario, Java test programs with complex syntax and semantic dependencies still have problems with coarse granularity and poor reduction effects, resulting in high comprehension costs even after reduction. Therefore, this paper proposes a fine-grained test program reduction method, called JavaPruner, based on program constraints for Java test programs with complex program dependencies. JavaPruner first designs a fine-grained code measurement method at the statement block level, and then introduces dependency constraint relationships between statement blocks based on Delta Debugging to reduce the test program. This work targets Java bytecode test programs, and selects 50 test programs with complex dependencies from existing test program generation tools for JVM testing as the benchmark dataset to evaluate the effectiveness of JavaPruner. Experimental results show that JavaPruner can effectively reduce redundant code in Java bytecode test programs. Compared to existing methods, the reduction capability can be improved by an average of 37.7% on all benchmark datasets. At the same time, JavaPruner can maximize the reduction of Java bytecode test programs to 1.09% of their original size while ensuring program effectiveness and defect detection ability, effectively reducing the analysis and comprehension costs of test programs.